The United States is a country of religious diversity. Unlike many other countries, there has been no “state church,” except for a few periods in some of the early colonies. To know and understand your ancestors, you will want to learn about their religious faith. To locate records kept by their church, you may need to learn the history of the denomination.

The first major group of Roman Catholics to live in what is now the United States started a colony in Florida in 1565. Beginning in 1598 Roman Catholics also began to settle areas that are now states along the Mexican border. Other Roman Catholics from England settled in colonial Maryland before 1649. Louisiana was settled by Spanish and French-Canadian Catholics in the 1700's. By 1850 the Catholic Church had the largest church membership in the United States. Much of this growth was due to immigration of Catholics from Ireland and other countries. In the late nineteenth century, millions of Roman Catholic immigrants came from southern and eastern Europe. In addition, most Hispanic immigrants also belonged to the Catholic Church. The largest Catholic groups settled in major cities.

In 1660 approximately 75 percent of the total population of the thirteen British colonies was either Anglican or Congregationalist. The Anglican Church (the Church of England, also known as Protestant Episcopal or Episcopal) was well-established in Virginia and a few other English colonies.

The Puritans who established the Massachusetts Bay Colony and the Separatists of Plymouth Colony were the first of many groups known as Congregationalists. Several of these congregations later united to become either the Disciples of Christ, the Christian Church, or the United Church of Christ.

Seventeenth and eighteenth century immigrants from Scotland and Northern Ireland brought Presbyterianism to Pennsylvania and later to many of the middle and southern colonies. By the mid-eighteenth century, Presbyterianism had nearly as many members as the Anglican and Congregationalist churches.

Members of the Society of Friends (often referred to as Quakers) began immigrating from England, Wales, and Germany in the late 1600s. A large group of Quakers settled near Philadelphia. By 1700 the Society gained considerable influence in most of the New England and middle-Atlantic colonies. Quaker migration to the southern colonies, especially North Carolina, continued until the Revolutionary War when the strength of the Society began to decline. Many Quakers left the southern states and migrated primarily to Ohio, Indiana, Illinois, and Canada.

Several groups of the Evangelical, German Reformed, and German Lutheran faiths settled in Pennsylvania in the 1700's. At the same time, several small groups of German Pietists, such as the Mennonites, Dunkards, Brethren, and Amish also arrived in Pennsylvania. Groups of Dutch Reformed from Holland became well-established in New York and New Jersey in the mid 1600's.

The nineteenth century was a period of church growth, diversity, and division. Millions of new immigrants reshaped American religious life. For example, large numbers of German and Scandinavian (particularly Swedish) immigrants established many Lutheran congregations, especially in the upper midwest states.

The Baptist religion, established in colonial Rhode Island, became the largest Protestant denomination in the United States by the early 1800's, when many Baptist churches were organized throughout the middle-Atlantic and southern states. The Baptists again became the largest Protestant denomination after 1920.

By 1850 approximately one-third of all American Protestants were Methodists. From about 1820 to 1920 Methodism was the largest Protestant denomination.

Many Jewish immigrants have also been attracted to America's largest cities. The ancestors of most American Jewish families arrived in the late nineteenth and early twentieth centuries. These included many immigrants from eastern Europe, particularly Austria and Russia.

The Church of Jesus Christ of Latter-day Saints (also known as the Mormon Church) was organized in New York in 1830. Latter-day Saint communities were established in Kirtland, Ohio, central western Missouri, and Nauvoo, Illinois, before the main group of the Church migrated to the Intermountain West. By 1900, there were LDS settlements in Utah, Nevada, Arizona, Idaho, Wyoming, Colorado, California, Mexico, and Alberta, Canada. The Tracing LDS Ancestors Wiki page gives more information about records of The Church of Jesus Christ of Latter-day Saints.